The wording on it says when any unit falls below half health she gets the turn meter. That should still be the case if multiple people fall below half health including the enemy team. But if you read JKA unique its says when units fall below half health or is defeated, Talzin doesnt say "or is defeated" so going from 51% to dead in 1 hit shouldnt give TM.
Also any time the character goes below 50% and doesnt insta die it should count so a resurrect assist knocking the damage down should have the same effect.